Intelligent toll telephone system and method

Abstract

A toll telephone coupled to tip and ring conductors of a toll trunk and through which various toll signals flow between a central office and the telephone (such as a coin ground signal to indicate the presence of the coin) has a hook switch with an off-hook condition for instituting the flow of loop current. To allow local, coin-free calls, the telephone has electronic circuitry for applying a simulated coin ground signal to the tip conductor continuously during the off-hook condition to permit coin-free calls to be made from the toll telephone. Additionally, the telephone includes a single relay system for providing an open-loop coin check responsive to a corresponding signal from the central office. The telephone provides a notch filter for discriminating against one of the multiple frequencies of a bong tone, thus allowing the remaining frequency to be detected.

What is claimed is: 
     
       1. A toll telephone for use in a telephone system with a central office having a toll trunk including tip, ring and ground conductors coupled to said telephone and through which various toll signals flow between said central office and said telephone including a coin ground signal to indicate the presence of a coin, said toll telephone comprising: a hook-switch having an off-hook condition for instituting the flow of loop current through said toll telephone from said tip and ring conductors; and   means at said telephone for applying a simulated coin ground signal to said tip conductor continuously during said off-hook condition or momentarily as a result of an open loop coin check to permit coin-free local calls to be made from said telephone.   
     
     
       2. The toll telephone recited in claim 1 wherein said means for applying a simulated coin ground signal comprises an electronic simulated inductive circuit means having a relatively low direct current resistance and a relatively high alternating current impedance. 
     
     
       3. The telephone system recited in claim 1 further comprising a coin escrow relay and means at said toll telephone for sensing coin conditions and operating said escrow relay for coin collection or refund. 
     
     
       4. The toll telephone recited in claim 3 further comprises means including a single relay switching in either said escrow relay or said simulated inductive circuit means during either the open loop type coin check interval or continously in a continuous ground type system. 
     
     
       5. The toll telephone recited in claim 1 further comprising: coin totalization means at said telephone;   means for deenergizing said telephone following completion of said off-hook condition; and   means for latching said coin totalization means during deenergization of said telephone.   
     
     
       6. The toll telephone recited in claim 1 wherein said central office toll signals include a multiple frequency bong tone and wherein said telephone further comprises means including a notch filter for discriminating against one of said multiple frequencies while the remaining frequency is detected by way of a zero crossing detector means, for detecting said bong tone. 
     
     
       7. A toll telephone for use in a telephone system with a central office having a toll trunk including tip and ground conductors coupled to said telephone and through which various toll signals flow between said central office and said telephone including a multiple frequency bong tone, and wherein said toll telephone comprises means including a notch filter for discriminating against one of said multiple frequencies and the remaining frequency is detected by a zero crossing technique for detecting said bong tone. 
     
     
       8. A toll telephone for use in a telephone system with a central office having a toll trunk including tip and ground conductors coupled to said telephone and through which various toll signals flow between said central office and said telephone including an open-loop coin check, said toll telephone comprising means providing ground through an escrow relay on an simulated inductor circuit during the open loop coin check interval or for the duration of the call in a continuous ground type system. 
     
     
       9. A method for operating and completing local calls on a coin telephone without inserting a coin, wherein said telephone is used in a telephone system with a central office having a toll trunk including tip and ring conductors coupled to said telephone and through which various toll signals flow between said central office and said telephone including a coin ground signal to indicate the presence of a coin, said method comprising the steps of: providing a hook switch having an off-hook condition for initiating the flow of loop current through said toll telephone between said tip and ring conductors; and   applying a simulated coin ground signal at said telephone to said tip conductor continuously during said off-hook condition to permit coin-free operation of said toll telephone in a continuous ground type system.   
     
     
       10. The method recited in claim 9 further comprising the steps of: providing a coin escrow relay at said toll telephone; and   sensing coin conditions at said telephone and operating said escrow relay from said telephone for coin collection or refund.   
     
     
       11. The method recited in claim 9 further comprising the steps of: providing coin totalization means at said telephone;   deenergizing said telephone following completion of said off-hook condition; and   latching said coin totalization means during deenergization of said telephone.